Various portable or semi-portable machines are known which dispense roofing washers individually onto roofing material, such as a blanket of roofing insulation or a roofing membrane, and which drive a fastener having a head, such as a screw, through the central aperture of such a washer, through the roofing material, and into an underlayment, such as a wooden roof or a corrugated metal roof, until the fastener bears against the washer. Herein, terms such as "roof" and "roofing" are to be broadly understood, so as to cover roofs, decks, ceilings, and similar structures.
Such a portable or semi-portable machine is exemplified in Boegel U.S. Pat. No. 4,246,939 wherein different mechanisms are disclosed (see FIGS. 19, 20, and 21, and FIG. 22) for dispensing washers individually from a stack of washers in a magazine. In such a portable or semi-portable machine, it is known to place a weighted plunger onto the uppermost washer in the stack to restrain the washers in the stack from cascading from the stack if the magazine is tipped so as to tip the stack.
Another such machine is exemplified in Mays U.S. Pat. No. 4,657,167 wherein different mechanisms are disclosed (see FIGS. 3, 4, and 5 and FIGS. 6 through 10) for dispensing washers (which therein are called washer-like plates or disks) from a stack of washers in a magazine. No provision is disclosed to restrain the washers in the stack from cascading from the stack if the magazine is tipped so as to tip the stack. Tipping is required (see column 4, lines 31 through 36) to allow laterally mounted wheels of the disclosed machine to roll on an underlying surface.
Roofing washers of particular interest are disclosed in Dewey U.S. Pat. Des. 263,678, Dewey U.S. Pat. Des. 263,927, and Dewey U.S. Pat. Des. 263,928, which are assigned to Illinois Tool Works Inc. of Chicago, Ill., the assignee hereof. Each such washer has a central aperture, which is adapted to receive a fastener, and is embossed with a pattern of ribs so as to have positive relief and planar areas on its upper face and negative relief and planar areas on its lower face. The ribs on such washers are functional, as well as ornamental, since the ribs strengthen and rigidify such washers, which can be thus made from thin blanks.
Ordinarily, when stackable washers, such as those according to any of the Dewey patents noted above, are made in a mechanical or hydraulic press employing metal-working dies, a lubricating medium is used which tends to leave some residue on each washer. It is uneconomical to clean such residue from each washer. Because such residue tends to be somewhat adherent, and because such washers tend to be tightly stacked, it is difficult to dispense such washers individually in a washer-dispensing machine, since a plurality of such washers tend to be simultaneously displaced from a stack of such washers in such a machine, whereby the machine can become jammed.
Although the washers noted above are typically square, except for rounded corners, circular roofing washers and oblong roofing washers also are known. Circular roofing washers have particular utility with roofing membranes, which tend to be easily punctured.
Washers with countersunk apertures are preferred for overlying more compressible material, such as a blanket of roofing insulation, whereas washers without countersunk apertures are preferred for overlying less compressible material, such as a roofing membrane, which would be typically applied over a blanket of roofing insulation. It is desirable to countersink the heads of fasteners used to fasten a blanket of roofing insulation to an underlayment, if a roofing membrane is to be later applied over the blanket of roofing insulation, in an effort to avoid puncturing the roofing membrane where the fastener heads would underlie the roofing membrane and where a worker might step carelessly or unwittingly.
Stackable washers according to Dewey U.S. Pat. Des. 268,678, as produced from steel blanks and embossed to countersink their central apertures relative to positive relief on their upper faces and negative relief on their lower faces, and as sold by ITW-Buildex (a division of Illinois Tool Works Inc.) of Itasca, Ill., have enjoyed commercial success in the United States in recent years.
Also of particular interest, screw guns equipped with screw-feeding attachments, so-called stand-up screw guns, are exemplified in Murray U.S. Pat. No. 3,960,191, Dewey U.S. Pat. No. 4,236,555, and Dewey U.S. Pat. No. 4,397,412, which are assigned to Illinois Tool Works Inc., the assignee hereof. Such stand-up screw guns, as known heretofore, are not capable of dispensing washers but are used to drive screws through central apertures of manually placed washers, through roofing materials, and into underlayments. Such stand-up screw guns, as sold by ITW-Buildex (a division of Illinois Tool Works Inc.) of Itasca, Ill., under its ACCUDRIVE XL trademark, have enjoyed commercial success in the United States in recent years.
Although known portable or semi-portable machines which dispense roofing washers individually onto roofing material, such as a blanket of roofing insulation or a roofing membrane, and which drive a fastener having a head, such as a screw, through a central aperture of each washer, through the roofing material, and into an underlayment, such as a wooden roof or a corrugated metal roof, until the fastener bears against such washer, have proved to be generally satisfactory, there has been a need for an improved machine having such capabilities. Moreover, there has been a need for an improved, stackable washer, which is dispensable by such a machine.